Asthma complicates 1-2% of pregnancies and has been associated in retrospective studies with an increased incidence of adverse perinatal outcomes. However, existing information regarding the effect of gestational asthma on pregnancy and the infant is inadequate to define intervention stratagy or guidelines for the optimal management of asthma during pregnancy. This study is based on the assumption that the prior reported increased adverse outcomes were due to inadequate disease control and prospectively tests the hypothesis that asthma which is adequately controlled during pregnancy by carefully chosen medications does not increase the risk of perinatal complications or the incidence of adverse infant medical, developmental or cognitive outcomes. Two groups of pregnant women will be studied: A. Active asthma - Pregnant women with active asthma will be identified, prospectively managed using specific therapeutic guidelines, and serially evaluated using symptom and medication diaries, physical examination and spirometry. B. Control - Pregnant women with no history or symptoms of asthma who match an asthma patient on the basis of age, parity and smoking habits will enter the "Control" group during the first trimester. The following parameters will be compared in Group A patients whose disease was adequately controlled during pregnancy based on specific criteria versus Group B subjects: Characteristics and complications of pregnancy, labor, delivery and post-partum; newborn characteristics and abnormalities; and medical, development and cognitive characteristics of the 1 year old infants. These parameters will also be compared in subgroups of asthma patients defined on the basis of degree of asthma control determined by objective criteria as well as subgroups based on asthma medication useage. By defining the effect on pregnancy and the infant of gestational astham which is adequately controlled by selected asthma medications, this study should lead to more rational management of asthma during pregnancy and thus help to optimize the health of pregnant women with asthma and their babies.